Superposition and Coherence & Stationary (Standing) Waves Flashcards
When does Superposition happen?
When two or more waves pass through each other
What is the Principle of Superposition?
That when two or more waves cross, the resultant displacement equals the vector sum of the individual displacements
What two different types of Interference are there?
Constructive + Destrcutive
When two or more waves superpose with each other, the effect is called [………..]
Intereference
What happens when two crests interfere?
Gives a bigger crest (Constructive Interference)
What does a trough plus a trough give?
Bigger trough (Constructive Interference)
What does a crest plus a trough give?
Nothing (Destructive Interference)
Which two points with a phase difference of a certain value are in phase?
zero or a MULTIPLE of 360 (degrees) 2π
Which two points with a certain phase difference values are exactly out of phase?
Odd-Number multiples of 180 (degrees) π
To get interference patterns the two sources must be […………]
coherent
What is meant by Coherent Sources?
They have the same wavelength and frequency and a fixed phase difference between them.
Constructive or Destructive Interference depends on the [……………….]
path difference
What is this term called? ‘The amount by which the path travelled by one wave is longer than the path travellled by the other wave’
Path Difference
What is the Constructive Interference Path Difference?
n λ (where n is an integer)
What is the Destructive Interference Path Difference?
(n + 0.5) λ
Show the apparatus used the observe interference with sound waves.
Describe how you can observe interference with sound waves.
- Connect speakers to the same oscillator and place them in line with each other
- Walk slowly across the room in front of them
- You will hear varying volumes of sound. At the points where the sound is loudest, the path difference is a whole wavelength
- The sound will be quietest at points where the path difference is an odd number of half wavelengths
Diagram showing waves in phase.
Are points A and B in phase on the diagram?
YES
Are points A and C in or Out of Phase?
Out of Phase
When do you get Stationary Waves?
When a Progressive Wave is Reflected at a Boundary
What is the PROPER definition of a Stationary Wave?
A stationary wave is a superposition of two progressive waves with the same wavelength, moving in opposite directions
Is energy transferred in a Stationary Wave?
No energy is transferred
What are Nodes?
where the amplitude of the vibration is zero
What are AntiNodes?
Are points of maximum amplitude
